This invention relates to a control device for an eddy current retarder having a number of energizing windings, the device having a number of electrical contactors adapted to provide sequential control of the energization of as many windings or groups thereof in the retarder as there are contactors.
The invention relates more particularly to such a control device which comprises: an insulating support; a plurality of connecting terminals mounted on said support for connection to respective retarder windings; a junction terminal mounted on said support for connection to one pole of a power supply; a plurality of contactors corresponding to said connecting terminals; each said contactor comprising first and second fixed contact members, a bridge contact co-operating with said first and second fixed contact members, and a pull-on contactor winding controlling said bridge contact; a first contact element to which said first fixed contact member is secured and which is connected to the corresponding connecting terminal; a second contact element to which said second fixed contact member is secured and which is connected to the said junction terminal; and a plurality of control terminals each connected to a corresponding contactor winding and for connection to a control selector for consecutively energizing said control terminals.
In known forms of such control devices, such as that described inter alia in the Applicants' Certificate of Addition FRANCE No. 70.46639 filed on Dec. 24 1970, with reference to FIG. 2 thereof, the insulating support or base has the general shape of a horizontal plate carrying three parallel rows of elements, viz. a row of contactor windings topped by their associated bridge contacts, a row of insulating fittings or mountings topped by fixed contact members adapted to cooperate with the bridge contacts and a row of terminals which extend over the whole width of the base near one of its edges.
By way of flat wiring below the base or support, the terminals are connected to the respective winding ends and to the fixed contact members and have connected to them flexes enabling all the contactors to be connected to the outside circuits by which they are controlled and which they control.
The unit embodied by the support or base member and the various elements thereon is received in a protective casing or box which has a removable cover, a chamber in the box between the bottom thereof and the support member being reserved for special components of the contactor control and protection circuits.
A known device of this kind has a number of disadvantages, more particularly the following:
The device occupies a considerable height, for the relatively high contactor windings take up only some of the support, so that space is wasted above the terminal row.
The space available below the support to receive the control and protection circuits is very low and therefore difficult of access.
The height of the windings means that the insulating mountings or fittings, which carry the fixed contact members so that the same are offered up opposite to the bridge contacts, must themselves be relatively high, so that it is difficult to position the supported fixed contact members accurately even though the mountings may be very rigid and firmly fixed to the support.
The presence of the insulated mountings leads to the existence of a relatively large distance and a relatively large number of items between each fixed contact member and the terminal corresponding thereto, with the possible result of unsatisfactory voltage drops.
Because of the extent of the terminal row and of its nearness to the support edge, the conductors connecting such terminals to the outside are virtually impossible to group together before leaving the casing in bunches which can extend through lead-outs or glands in the casing or which are suitable for making a simple and reliable connection by multiple-pin connectors.